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  1. #1

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    How well does a digital camera`s TTL metering translate to a 4x5 camera?

    Hey guys. I`m having a lot of trouble coming up with exposure times. One of the problems is that I`m certain that the light meter I`m using isn`t giving me accurate enough times. This is because I`m trying to use it to meter through ND filters (edit: not real ND filters but a welders glass), which I can`t put flush up to it, resulting in a 3/4 inch gap between filters and meter, allowing extraneous light to come between them, throwing off the metering. So what I`ve thought about doing is just putting the filtering setup I`ll be using onto my digital SLR camera and using it to get the metering, then just use that. But I want to know how close the metering will translate onto the 4x5 camera. I`ve done this with my medium format camera and it worked quite well, but this is really my first time with a large format.

    What do you guys think?



    Oh ya, do shutter speeds just start doing the exact opposite once it hits 1 second? like 1s, 2s, 4s, 8s, 15s, 30s, 60s, 125s, 250s, 500s

    Thanks.
    Last edited by Treymac; 10-11-2010 at 08:11 PM. Click to view previous post history.

  2. #2
    dehk's Avatar
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    Why don't you just do the math? The filter tells you how many stops it cuts down.

    Shutter speed, yes it does, but you have to worry about reciprocity failure for long exposures. Most manufactures will have this data in their data sheet for the specific film online.

    Cheers
    - Derek
    [ Insert meaningless camera listing here ]

  3. #3

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    Hey. Sorry, I was going to try to update my post but the forums were having problems for a second.

    I`m not actually using real ND filters but a welders glass, which is somewhere around 10 stops, but who really knows. So I`m only left with trying to meter for it, and this is the problem.

  4. #4
    Sirius Glass's Avatar
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    Welder's glasses are not ND filters. That is your first problem.

    Steve
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  5. #5

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    Quote Originally Posted by Sirius Glass View Post
    Welder's glasses are not ND filters. That is your first problem.

    Steve
    Thanks for the tip, I thought welders glass really was an ND filter /s. They have the same effect, but are much stronger with a little less clarity. And a lot cheaper.

  6. #6
    JBrunner's Avatar
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    Honestly interested why anyone would need to cut ten or so stops with a large format camera? The problem is usually the entire opposite. In any case you can use another cameras TTL to determine the density of the camera, digital or otherwise, as long as you meter a uniform subject, like a grey card or similarly neutral field. In addition to not being optically correct, I'm pretty sure a welders glass isn't anything close to neutral. Density aside, most likely the result on B&W will emulate using a #11 or thereabouts. Might work for a few things, really ugly for most. Hideous for color unless you're photographing algae. Probably not worth the bother, but you seem determined. I'll be curious of the results.
    Last edited by JBrunner; 10-11-2010 at 08:35 PM. Click to view previous post history.

  7. #7
    dehk's Avatar
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    Quote Originally Posted by Treymac View Post
    Hey. Sorry, I was going to try to update my post but the forums were having problems for a second.

    I`m not actually using real ND filters but a welders glass, which is somewhere around 10 stops, but who really knows. So I`m only left with trying to meter for it, and this is the problem.
    As the other poster said, welder's glass are not ND glass. But, i take it you do not have a spot meter to stick it right at the glass. Well, in that case, yeah try to meter with your SLR. Even with multi zone / matrix metering as long as its the same scene. Good luck. Or alternatively, spot meter to something with and without the glass to like a grey card, so you know how many stops its cutting off and you can just do the math the next time.

    If anything it will be interesting.
    - Derek
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  8. #8

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    Ok, thanks a lot. I`v been curious about that for a long time. I`m trying to get a long exposure to still the ocean and capture the movement of the clouds.

    One thing I`ve been thinking about also is that since I do have 2 ND 0.6 and 1 0.9, stacking them together will give me 7 stops. The reason I didn`t think about going this route is that the welders glass is just one piece of plastic, while the filters are 3, kind of a toss up of which is worse doing optically. But I figured that using the actual filters with a metering of f5.6 @ 1/60, applying them will give me 2 seconds. And that`s not long enough. But I never considered adjustments. Tell me if I`m correct. With a reading of f5.6 @ 1/60 the filters give me f5.6 @ 2s. Going f8 @ 4s because of less light through the aperture, I have to keep the shutter open. Continuing, f11 @ 8s. Finally, f16 @ 15s. And 15 seconds is around the time that I want.

    Is that correct, my brain hurts now. I always get flustered and make stupid mistakes when I`m starting with something completely new.

  9. #9
    JBrunner's Avatar
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    Quote Originally Posted by Treymac View Post
    Ok, thanks a lot. I`v been curious about that for a long time. I`m trying to get a long exposure to still the ocean and capture the movement of the clouds.

    One thing I`ve been thinking about also is that since I do have 2 ND 0.6 and 1 0.9, stacking them together will give me 7 stops. The reason I didn`t think about going this route is that the welders glass is just one piece of plastic, while the filters are 3, kind of a toss up of which is worse doing optically. But I figured that using the actual filters with a metering of f5.6 @ 1/60, applying them will give me 2 seconds. And that`s not long enough. But I never considered adjustments. Tell me if I`m correct. With a reading of f5.6 @ 1/60 the filters give me f5.6 @ 2s. Going f8 @ 4s because of less light through the aperture, I have to keep the shutter open. Continuing, f11 @ 8s. Finally, f16 @ 15s. And 15 seconds is around the time that I want.

    Is that correct, my brain hurts now. I always get flustered and make stupid mistakes when I`m starting with something completely new.
    You get to 15s and you'll need more exposure than you are calculating. For instance with FP4 if a 15s exposure is indicated, I expose for around a minute. You have plenty of ND on hand for what you want to do. Forget about the welders glass and look up reciprocity.
    Last edited by JBrunner; 10-11-2010 at 09:56 PM. Click to view previous post history.

  10. #10

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    Quote Originally Posted by JBrunner View Post
    You get to 15s and you'll need more exposure than you are calculating. For instance with FP4 if a 15s exposure is indicated, I expose for 60s. You have plenty of ND on hand for what you want to do. Forget about the welders glass and look up reciprocity.
    Ok, cool. I`m using Delta 100 so it`s fairly close.

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